The use of a catalyst, particularly in catalytic distillation columns, to carry out conjointly the chemical reaction and the separation of the products that are obtained is well known in the prior art. The catalyst can come in different forms and be placed inside the column in the form of bundles, in envelopes, or loaded or distributed on plates of a conventional type. A column can include, for example, a series of stages in which the chemical reaction and the separation of products are carried out.
Over time, the catalyst or else the product that takes part in a reaction loses the characteristic properties that are necessary and sufficient and that make it possible for the operation to be carried out, within a length of time that depends particularly on the frequency of its use and chemical or other reactions that are employed. Thus, it proves necessary to repeat it and/or to regenerate it to restore to it its initial properties so as to maintain the efficiency of the operations that are carried out inside the columns.
The prior art describes different ways to proceed.
The simplest way consists in halting the process and regenerating in situ the catalyst that is present inside the column and/or in replacing it. This method has, however, the drawback of having to halt the process and thus the operation of the column and, because of the amount of time involved in regeneration and replacement operations, leading to high costs.
Another way consists in unloading and in reloading the catalyst without halting the progress of the process, for example by following one of the methods that is described in patents U.S. Pat. No. 5,198,196, U.S. Pat. No. 5,510,089 or else U.S. Pat. No. 5,133,942.
These documents teach in particular a method that makes it possible to unload and load a catalyst in a distillation column during operation. For this purpose, the method, as it is described in one of the three patents, consists in drawing off from the distillation column all of the fluid that consists of at least the liquid phase passing through the catalyst and solid particles of the catalyst and sending the whole mixture to a separation device, at the end of which the liquid phase that is purified of the solid particles is sent to the distillation column and recycled until the entire catalyst is evacuated from the plate; the solid particles of the catalyst are then sent to a means that makes it possible to regenerate them, for example. The loading of the catalyst is done by using a liquid to form, with the solid particles of the catalyst, a "slurry," and said "slurry" is sent to the plates at which the catalyst was unloaded.
This method is well suited for replacing catalysts through which a fluid passes that consists of the liquid phase and the vapor phase or gas phase. It requires, however, means for separating the catalyst and the liquid phase, which can be bulky and which help increase the cost of the device.